Plastic impression material



UNITED STATES PATENT .OFFICE PLASTIC IMPRESSION MATERIAL Long Beach, 0alii., as-

produce the shape an ject. More particular] a material having original structure may The present applica part of my co-pendin ber 599,069, filed Ma Laurence E. Harrison,

sil'nor to Oramold Pr outs Corporation, West Hollywood, Calif., a corporation oi Nevada No Drawing. Application June 12, 1933,

Serial No. 675,461

d surface detail of such oby, the invention relates to pl tion is a continuation in g application Serial Numrch 15, 1932, for Plastic ,gums, and agaragar or the like, together with tri-ethanolamine soap, but which also metallic soap, the

is to be added.

contained a water-insoluble purpose of the tri-ethanol- An important objector the present invention ist production of the tissue. a A further obje as are sometimes a tooth and the inteeth. In this the present inct of the invention is to provide material which is easily and d, which will not deterioratewhich is not damaged by exlow temperature nd faithful remarginal portions of the gum posure to temp of water.,

Previously suggested eratures below the freezing point medium, such as saliva. 20

A further object of the invention is to provide an impression material having yielding or resilient properties as above mentioned, and being at the same time adapted to soften or become plastic upon heating, and which will retain its plastic condition during cooling to a sufiicien'tly as'not 'toburn or unduly heat the mouth ofth'e patient when placed therein, and to again solidify quickly and at a definite temperature, upon chilling, sufliciently to retain the exact shape of the impression after removal from the mouth. I A further object is to provide a material which has a very definite setting or jelling temperature, so that as the material is cooled to this temperature there is a rapid transition from the plastic or sol condition to the resilient or .gel" condition. By reason of this property, only a relatively small amount of chilling is necessary to cause the material to change completely from the one condition to the other. Consequently, the material may be applied to the teeth at a temperature only slightly above the setting temperature, and need be left in position in the mouth for only a relatively short time to provide complete setting, after which it may be withdrawn.

A further object of the invention is to provide a material which, after setting, is not susceptible to permanent plastic deformation even though stressed beyond the elastic limit, the material having the characteristic of breaking or cracking ifthe limit of resilience should be exceeded by a strain imposed during the removal thereof from the teeth, instead of undergoing a permanent deformation without breaking, as is plastic condition and the case with materials which depend upon the presence of rubber or the like for their resilience.

It is also necessary that the material, in order to be useful for the above certain other properties. Such material must have sufficient'body, cohesion, and toughness, so that when squeezed into small crevices and thereafter chilled it will retain its shape, thus enabling the dentist to obtain correct detail and measuremerits of the teeth and their relation to one another .and the gums. Furthermore the material should contract slightly upon chilling, while in beforesolidification or jelling has taken place, in order that a correct impression be obtained. 1

The material of the present invention relies principally upon a single constituent to obtain the desired setting or solidification at a temperature near but below body temperature, and I have found that agar-aga which in water solution jells outupon cooling to a-temperature of approximately 32 C. is quite suitable. "This one constituent however does not have properties which make it alone sufficient for compounding a dental impression material, in that the composition should be capable of developing considerable body upon cooling and before the solidification temperature is reached, and for this reason certain thermoplastic materials are also incorporated in the composition so that, as the composition is cooled, a gradual increase in body" is obtained up to a certain point, and then'the main solidification or jelling is realized. The term thermoplastic material as used herein will be understood to mean'a substance of one of the classes named below, which has the prop-,

erty of repeatedly changing from a non-plastic or solidified state to a plastic or fluent state, and back again, upon repeated heating and cooling through the temperature range encountered in dental technique Such materials are normally solid at'ordinarytemperatures and are also, in general, substantially non-volatile or of relatively low volatility, at temperatures up to 100 C. Any one or more of a number of thermoplastic materials may be utilized, and I prefer to include certain materials which also tend to increase the resilience or resistance to plastic deformation of the chilled mass,

The types of thermoplastic materials which may be used are as follows:

(1) Waxes, which serve to contribute to the body-development during cooling and also, dependent upon the kind of wax used, serve to control the degree of contraction obtained. during the body-development cooling stage. It has been found, generally, that the vegetable waxes effect a greater contraction than do the hydrocarbon waxes, and I preferably mix such vegetable and hydrocarbon waxes to obtain the del sired degree of contraction.

asfcopal gum and particularly, ofcopel-gums which are known to the trade as (2) A balata-like substance, such as guttapercha, balata, chicle or a balata-like. rubber isomar such as is obtained by. treatment of rubber'with sulphuric acid or the like. (3) A resin or resinous gum, for example, such those varieties passa e: gum inubsl and Manila gum".

-- 'ihe latter types of thermoplastic materials headings (2)' and (3) serve to effect 'j-development and also serve to impart and may he varied in relative proportions to purpose, shall have I may be, and preferably is,

obtain the desired properties, in the finished composition, as hereinafter set forth. The thermoplastic materials above-mentioned are, in general, water-insoluble, and are homogeneously distributed throughout the finished 5 I composition by emulsificaticn thereof with the aqueous phase containing the gel-forming material.

The composition also includes an oleaginous material which acts as a softening or modifying 10 agent for some or all of the thermoplastic materials. The oleaginous'material preferably also contains a free fatty acid as and for the purpose hereinafter set forth. The oleaginous material incorporated in the 15 composition simultaneously with the incorporation of one or more of the thermoplastic materials.

I am aware of the fact that dental impression plastics have been hitherto suggested which in- 20 elude a reversible hydrocolloid, resins and waxes, but such of those compositions as I am aware of have required the use of a relatively large amount of a reversible vegetable gel-forming hydrocolloid as compared to the added. I have found that a superior material may be obtained by so compounding the several ingredients that a very definite and stable emulsification of the thermoplastic materials is obtained, and I am thus enabled to prepare com- 3 positions containing relatively large amounts of non-hydrocolloid material as compared with the prior suggested compositions, so that considerable enhancement of the desirable properties is ob-. tained." 35

The composition of the present invention consists of an intimate emulsified mixture of the following ingredients, preferably in the following approximate proportions:

substances selected from the group comprising waxes, balata-like substances and resins or resinous gums 350 to 700 The composition preferably also includes, as an additional ingredient e. Vulcanized rubber filaments, 1 to- 3% of total of above ingredients The oleaginous constituent may be any suitable material such as a vegetable, animal or mineral oil, or a fatty acid, or mixtures of such materials, and I prefer to use a tri-ethanolamine soap as an emulsifying agen Theemulslfying agent may be incorporated in the mixture as such, if desired, or nay be formed during the compounding, for example, by using an oleag'inous material containing a free fatty acid and adding tri-ethanolamine to the mixture at a suitable point in the compounding procedure. For example, I may use anoleaginous material containing stearic, palmltic or oleic acid, or, as a specific example, I may use an oleaginous material such as resin oil, which contains an appreciable amount of abietic acid. It will be appreciated that 'tri-ethanolamine may be caused 7 amount of other materials 25 to react with the abietic acid to form tri-ethanolamine abietate, which I have foundto be a desirableemulsifying agent, the preferred properties of which will be subsequently described.

The thermoplastic, material, as above pointed out, preferably includes both'a material adapted to control the development of a body" during cooling of the composition to solidification temperature, and a material which contributes to the resilience of the chilled composition, and thus the thermoplastic materials may comprise a hydrocarbon wax such as ceresin and/or vegetable waxes such as candelilla or carnauba, together with a water-insoluble resin such as Pontianak or semi-hard Manila gum or other materials such as gutta-percha, balata or chicle, or combinations of the first-mentioned with the latter-mentioned materials. In addition to, or in place of one of the latter-mentioned materials, I may use a balata-like isomer of rubber, such as may be produced by treatment of rubber at ,a suitable temperature with sulphuric acid or other sulphuric reagent, as described in Industrial and Engineering Chemistry, Vol. 19, pages 1325-33, December, 1927. The use of such rubber isomers constitutes a preferred embodiment of the invention, due to the superior strength and body of the material thus obtained. These isomers, having the general formula (CGHB)1|, are distinguished from rubber in that they are thermoplastic, and are superior to balata due to their greater toughness and strength. The proportion of thermopfastic material may be varied within limits to the end that the "body development and resilience of the resulting composition is controlled. Furthermore, the proportions of the several classes of thermoplastic materials may be varied within limits as will be understood by the art. When a material such as Pontianak gum or Manila gum is used. it may be dissolved in the oleaginous material, in some cases with the addition of alcohol or the like to improve the solution, and when a material such as gutta-percha, balata, chicle or a balata-like rubber isomer such as above described is used, I prefer to add it separate from the oleaginous material, preferably insolution in a suitable volatile solvent which may subsequently be removed by heating. I

In general, I prefer to use proportions of the several different classes of thermoplastic materials above-named, within the following limits:

Parts Wax 200 to 400 Balata-like substance 100 to 300 Resin or resinous gum 25 to 100 The reversible gel-forming hydrocolloid ,may be a suitable material such as agar-agar, and is preferably made into a water suspension or dispersion before adding to the mixture. Other aiginic gel-forming materials, such as Irish moss, may be used in some cases, but in general I prefor to use agar-agar, because of itsv definite setting temperature as a hydro-gel, and its absence of any appreciable tendency to take up additional water after it has once set. In some cases, I may use other reversible gel-forming hydrocolloids, such as gelatin, alone or in conjunction with an alginic substance.

Theamount of water used in the compounding is preferably closely regulated so that the desired consistency of the resulting composition is obtained. This water is preferably added'at certain points in the compounding procedure, as

hereinafter described, in order to provide the most advantageous results.

In addition to the above-discussed ingredients, I may add vulcanized rubber threads or the like,

which, when incorporated in the mass, contribute 5 materially to the strength and coherence thereof. Previously suggested compositions have included reinforcing filamentous or fibrous material such as silk floss, cotton fibres, wood fibres or the like, but it has been found that when such reinforcing materials are incorporated in' the compositions they exhibit a tendency to pull through the composition upon application of stress and thus lose some of their effectiveness in reinforcement where the material itself is quite elastic. For this reason I prefer to-provide a filamentous reinforcing material which is in itself elastic so that it will "give under resilient deformation of the composition. I have'found that vulcanized rubber filaments may be prepared by extruding raw rubber threads through fine apertures or nozzles into contact with suitable vulcanizing agents such as, for example, a solution of SzClz or SCI-2 or first into a vapor of SO: and

then into a vapor of H28. 'These vulcanized rubber filaments may be incorporated in the finished.

material before such material has cooled out of its sol condition and the addition of such elastic threads has been found to contribute materially to the stre gth and resistance to permanent deformation of the material. The material of the present invention which includes resilient rubber threads as above set forth is not to be confused with previously disclosed compositions containing unvulcanized rubber in the form of threads or the like, inasmuch as such compositions required the use of additional fibrous or filamentous materials to obtain the desired strength as the raw rubber did not possess the desired properties of strength. and resilience such as are possessed by vulcanized 40 rubber threads. The use of rubber threads as herein described does not detract from the characteristic exhibited by the material of breaking or rupturing upon application of stress such as to, deform the material beyond its ability to return to its original position, as the material will break and show fine cracks sufficient to warn the user.

Inaddition to the above ingredients the material also preferably includes a small proportion of scenting or flavoring constituents of such prop- 60 erties as to impart a pleasant taste and odor' to the material so that the use thereof is not disagreeable to the patient. I also prefer to add a certain amount of oil-soluble coloring material such as a red dye or the like, to improve the appearance of the composition. Certain plaster-hardening agents such as tannic acid, burnt alum or copper sulphate may also be incorporated in this mixture, if desired, for providing certain characteristics to the composition as regards subsequent production of plaster molds or the like, Other-advantageous materials may also be incorporated in. the composition for various purposes, such as for example: an antiseptic agent such as guaiacol, hexyl-resorcinol, boric acid or the like; a strengthening or reinforcing material such as wood-flour, silk or cotton fibres, or other suitable material of desirable characteristics. i

The materialsabove-described, when combined with one another in suitable manner, for example, as hereinafter set forth will produce a homogeneous mixture which does not segregate or show any tendency for any of the constituents to agglomerate. Furthermore, when these materials are properly combined the composition is character- 4- ized by having a relatively sharply defined solidifying point so that after being brought by heating tion thus possesses particular advantages as comtheir composition,

pared with comparable compositions which depend principally upon a mixture of waxes for in that the solidification extends over a relatively narrow temperature range,

be added while the wax compositions have a relatively wide softening range and have to be considerably super-cooled. after taking the impression to insure that all of the components will be solidified before removal from the mouth.

It has been found advantageousto use certain specific ngredients in certain approximate proportions, as hereinafter described, but will be understood that the invention in its broader aspects is not restricted to these specific ingredients and proportions, and the invention contemplates all such deviations and modifications as would occur to those skilled in the art.

As a specific example of the compounding of an embodiment of this invention, the following is an outline of the more advantageous approximate proportions of the several constituents, and the preferred method of mixing such ingredients to-- gether in order to provide a material combining to a high degree all of the above-mentioned desirable properties. According to this embodiment I take from 140m 200 grams for example, 150 grams of a mixture of resin oil and a hard gum such as Pontianak gum, to which is added approximately per cent (0.75 gram) of tri-et hanolamine. The proportion of resin oil to the gum may be varied between a ratio of 4:1 to 1:1, and may,

for example be in a ratio of 2:1. The amount of tri-ethanolamine added may be varied, for ex ample, from per cent to 1 per cent, dependent upon the quantity of emulsifying soap desired in the composition, as hereinafter more completely set forth. The above mixture is heated to about 100 C. and approximately grams of water is added, and the mixture thoroughly stirred to get auniform emulsion. I have found that when /2 per cent of trl-ethanolamine is added to the resin oil-gum mixture, approximately 60 per cent of water may be taken up in a true emulsion.

From to 200 grams, for example grams of balata-like substance, preferably a rubber isomer of the type above described, is then added, preferably in the form of a 2 5.per cent solution in benzol or other suitable solvent. This emulsifics in the above mixture and is homogeneously distributed therethrough. The heating is continued to drive off the benzol.

Following the emulsification of the mixture I add 2100 grams of an aqueous agar-agar solution containing 150 grams of agar-agar, thus providing a total of approximately 2050 grams of water in the composition. This material may warm if desired and upon agitation will emulsify in the above mixture to form a homogeneous mass.

To the above mixture is added 300 grams of wax, for example, a mixture of waxes comprising four parts 'ceresin and one part candelilia wax, which may be previously melted, which also emulsifies in the mixture. Advantageous results, for certain purposes, may also be obtained by adding 20 cc. of glycerol at this point in the comto have an average diameter on that threads from 2 mm. to

pounding, or the glycerol may be added to the aqueous agar-agar. r i

To the above mixture suitable amounts of flavoring, scenting and coloring material may be added, and 1 prefenalso to add approximately 0.4 gram of burnt alum which is uniformly distributed through the mass.

I also prefer to add approximately 55 grams of vulcanized rubber threads to the composition,

and such threadsare preferably so prepared as 10 the order oftbat of a silk or cotton fibre or less. The length of these threads may vary according to the particular requirements of the user, but I have found 20 mm. in length are quite satisfactory.

The amount of trl-ethanolamine which is added to the mixture of oil, fatty acid and gum determines the extent of saponiflcation ot the free fatty acid, which in amount of water which can be taken up to form a stable emulsion having substantially no tendency to take additional water at the temperature under which the material is ordinarily used. The body-development temperature range may 2 e in part controlled by the proportion or resin oil (or other oleaginous material) to the Pontianac or other gum and by varying the proportion of total water added to the-mixture; The proportion of tri ethanolamine should vary with 3 the amount of water to be taken up, to theend that a stable emulsion is obtained. The amount and character of the waxy materials which are added-also affects thebody-development temperature range of the mixture and the use of relatively soft or relatively hard waxes alone or intermixed, will affect the contraction of-the mass during the cooling thereof, and the rigidity of the solidified mass.

The above composition is ready for immediate use upon cooling to a suitable temperature for application to the mouth, or may be poured into, a mold and allowed to harden.

The completed material is solid at ordinary temperatures, but has a certain yielding or resilient property which enables impressions formed therefrom to be removed conditions such as above-mentioned, even after chilling to atmospheric temperature or below. At such temperatures, however, the material is not readily susceptible to permanent deformation at ordinary pressures and is adpated tov return to its original position when any force causing resilient deformation thereof is removed. If, however, an excessive deforming force is ex- 5 erted upon the material. permanent deformation will be accompanied by fracture or rupture, which will be apparent at the surface of the ma-r terial and thus warn the user that the impres sion has been damaged. The material has a good property of cohesion at all temperatures at which it is to be used and has a satisfactorily tenacious body or consistency which causes it to hold together while 'makingimpressiom and af ter removal thereof from the teeth.

The material or composition is of such a nature that solidification or-setting is obtained through a relatively narrow temperature range, so that the material does not haveto be cooled for an excessively long time after an impression is made to insure complete solidification. The body-development range may be confined to about 5 C. Upon'being-suitably heated above the solidifying temperature the material softens and becomes readily plastic and adapted to flow 7 turn determines the 20 from the teeth under under pressure and fill all recesses, crevices, and small indentations in the teeth and gums when .pressed into engagement therewith. Further-- more, the material pressed into position with the fingers without is not sticky and can be water at about 15 to 30 C.

The method of using this material is, in general, similar to other impression materials now in common use. The material of the presentinvention is preferably softened or rendered plastic by heating the same until it is sufficiently soft and plastic throughout to permit it to be placed in the usual tray or mold and inserted in the mouth and pressed against the teeth and gums in the usual manner. At the time the material is actually inserted in the mouth, the temperature.

thereof may be about 40 C. or slightly higher. The compound is pressed firmly into contact with the teeth and gums and is then permitted to cool.

. As the material is cooled toward the solidification point, a gradual increase in the body" of the material occurs, and at the same time a gradual contraction also occurs which serves to bring the impression material into close and firm contact with the impression surfaces. This contraction also serves to compact soft gum tissue and thus obtain a more satisfactory impression. The contraction exhibited by this material is not to be confused with the contraction or shrinkage which oo-incidentally accompanies freezing phenomena, as in the case of a crystalline material, in view of the fact that the contraction of the present material takes place before the solidification and while the material is 'still subject to plastic deformation. In other words, the contraction takes place during the body-development cooling range atwhich time the composition is easily deformed into position to closely engage the impression surfaces, tion serves to compact the material against such impression surfaces but upon solidification the mass is in an unstrained condition. After solidification the material is no longer subject to plastic deformation but may be resiliently deformed for removal so that it will yield sumciently to permit undercut, wedged, or thereof to be readily removed from the mouth and to then spring back to their original position, but is subject to rupture if over-stressed, as above described. After removal fromthe mouth, it may be used for the casting or molding of reproductions in plaster or other material. The material is of such nature as to produce very clean-cut reproduction and to produce extremely smooth surface casts in plaster or other material. Even in this state, however, the material has a certain amount of resilience and ability to'yield,

-which property may be advantageous for certain purposes. For example, this permits the impres- It has been found that a composition prepared 7 as above described is not subiect to damage by exposure to freezing temperatures (below 0 C.)

and this contracdovetailed portions inasmuch as it may, even after exposure to such freezing temperatures, be heated to softening temperature for use without diminution of its favorable characteristics.

The plaster-hardening agent such as tannic 5 acid, burnt alum or copper sulphate provides. a highly advantageous characteristic to the material in connection with the above-described casing or molding in reproductions in plaster. When the plaster is poured onto the impression, the 10 plaster-hardening agent present in the impression material causes a very rapid setting of the plaster at the immediate surface of the impression material, so that a very faithful reproduc-' tion of the surface contours of the impression and 15 a hard-surfaced casting is obtained by the plaster and there is no tendency for the plaster to shrink away from the mold surface as setting thereof progresses.

I claim:

1. A dental impression material comprising an emulsified mixture of an oleaginous material, an emulsifying agent, a reversible gel-forming hydrocolloid, water, a wax, a balata-like thermoplastic substance, and a thermoplastic resin or 25 resinous gum.

2. An impression material comprising an intimate mixture of:

, Parts An oleaginous material to 150 30 An emulsifying agent to 1% A reversible gel-forming hydrocolloid to 175 Water 2000 to 2500 Thermoplastic material 350 to 700 35 3. An impression material comprising an intimate mixture of:

Pa'rts An oleaginous material 75 to 150.- An emulsifying agent to 1% 40 A reversible gel-forming hydrocolloid 125 to 175 Water 2000 to 2500 A wax 200 to 400 r A balata-like substance 100 to 300 A resin or resinous gum 25 to 100 4. A dental impression material comprising an emulsified mixture of oleaginous material, an alginic gel-forming material, a tri-ethanolamine 5 soap, water, a wax, a balata-like thermoplastic resin or resinous gum.

5. An impression material comprising an intimate mixture of resin oil containing a constituent capable of saponification with tri-ethanol- 55 amine, tri-ethanolamine, an alginic gel-forming material, water, copal gum and a wax.

6. The composition set forth in claim 5, and comprising in addition a balata-like thermoplastic material. 60

7. A dental impression material comprising an emulsified mixture of oleaginous material containing fatty acid, tri-ethanolamine, a reversible gel-forminghydrocolloid. water, wax, a balatalike thermosplastic substance, and a thermoplas- (:5 tie resin or resinous gum.

8. An impression material comprising an intimate mixture of oleaginous material containing a free fatty acid 100 parts, tri-ethanolamine 0.75 part, agar-agar parts, water 2050 parts, copal gum 50 parts, waxes 300 parts.

9. An impression material comprising an intimate mixture of resin oil 100 parts, Pontianak gum 50 parts, tri-ethanolamine 0.75 part, a thermoplastic rubber isomer 150 parts, agar-agar 150 7 6 parts, water 2050 parts, ceresln wax 240 parts, and candelillawax parts, said resin oil 0on taining abietic acid.

10. An impression material comprising an oleaginous material, agar-agar, a balata-like substance, a resin, and a wax, emulsified in water in the presence of tri-etl anolamlne abietate. ,11. An impression material comprising an intimate mixture of oleaginous material containing a free fatty acid parts, trl-ethanolamine 0.75 part, agar-agar 150 parts, water 2050 parts, copal gum 50 parts; waxes 300 parts, and vulcanized rubber filaments from one tothree per cent of the total.

12. An impression material comprising an intimate mixture of resin oil containing abietic acid, 100 parts; Pontianak gum, 50 parts; tri-ethanolamine, 0.75 part; a thermoplastic rubber isomer,

13. An impression material'comprising an in- 5 timate mixture of: V

Parts An oleaginous material '15 to 150 ,An emulsifying agent to 1% A reversible gel-forming hydrocoll0 loid to 1'75 Water 2000 to 2500 Thermoplastic material 350 to' 100 Resilient vulcanized rubber filaments, 1-3 per cent of total or 10 above ingredients.

LAURENCE E. HARRISON. 

